Notably, 49 genes (e.g., AKT1, TUBB, HDAC1, and HIF1A) were widely expressed in most cell types (criteria: significantly expressed in at least five cell types), while nine genes (TOP2A, AURKA, AURKB, CDK1, PLK1, TYMS, DHFR, GMNN, and RRM1) were more specifically detected in osteosarcoma cells, especially in proliferating osteoblastic osteosarcoma cells (Figures 4G and S6I–O). Here, DHFR is linked to osteosarcoma.